This invention relates generally to an improved method and apparatus for the continuous space dyeing of yarn. More specifically, this invention relates to a method and apparatus for spraying dyes or other patterning liquids onto a moving yarn sheet in which a yarn sheet drive roll and liquid application jets are coordinated to provide for the application of several different liquids in accordance with a predetermined pattern and with precision registration, thereby providing the ability to apply such liquids to the moving yarn sheet with no unintended untreated or overlapped sections, and in which the dye that passes through the yarn sheet is collected and recirculated for reuse.
The production of yarn having different dyes spaced along its length is termed xe2x80x9cspace dyeing.xe2x80x9d Space-dyed yarns are desirable because they easily may be formed into textile fabrics that have an inherent random or pseudo-random pattern imparted by the patterning of the yarns comprising the fabric. While other methods of imparting a similar pattern to textile fabrics are well known, they are more difficult and require more steps than the present invention.
Several methods for space dyeing of yarns are known. Among batch-type processes (in which a predetermined quantity of yarn is treated at one time), for example, it is known to inject yarn packages with a number of different colored dyes to yield a space-dyed product. However, such batch processes are often more costly and require more product handling than continuous processes. Continuous space-dyeing processes (in which moving yarns are individually or collectively treated) are also known. Typically, dye may be applied by a series of rollers, or may be sprayed on individual yarns or yarn sheets. While generally more efficient than package dyeing techniques, these continuous dyeing processes often experience difficulties with dye mist and drips, resulting in unwanted marks and wasted dye liquor. Furthermore, dye overspray from the various colors being applied often mixes together in a single collection system and must be discarded, resulting in added costs for replacement dye as well as for waste handling and disposal.
In addition to the problems recounted above, none of these methods has been able to solve the problems of imperfect registration of the dye pattern. That is, often the yarns produced by these methods exhibit undesirable undyed areas, or areas in which an overlapping of different dyes results in undesirable colorations. Attempts to eliminate undyed areas by providing a constant overspray of dye have resulted in the use of more dye than the instant invention, resulting in a higher cost per pound of yarn, in addition to the necessity of adjusting dye formulations to compensate for the color imparted by the overspray. Such attempts also tend to exacerbate the problem of undesirable overlapping of adjacent dyed areas, and lead to space-dyed yarns in which the overall result is neither predictable nor controllable.
The present invention improves upon the methods discussed above. This invention may be used to apply any type of liquid colorant or patterning agent, including, but not limited to, acid dyes, disperse dyes, or pigments, as well as liquids other than dyes, to a moving yarn sheet. Any liquid yarn treatment agent, including, but not limited to, dye resists, water resists, finishing chemicals, or other treatments may be applied. Liquids may be applied at ambient temperature, or the temperature may be manipulated as desired or required for a particular chemical. Thickeners may be added to the liquids to alter the viscosity as desired or required. For illustrative purposes only, the invention will be described using the application of liquid dyes at ambient temperature. A yarn sheet passes over a yarn driven roll equipped with a sensor which tracks the position of the sheet as it passes through the dyeing apparatus of the instant invention.
Dyeing is controlled by a computer which is programmed to selectively activate and de-activate dye jets in accordance with pattern data in response to position data from the sensor. In this way, dyes are applied precisely at pre-specified locations along the length of the moving yarn sheet. Dyeing takes place when the computer generates a signal that causes an air valve to open, forcing dye liquor from a recirculating dye system to be formed into droplets that are sprayed onto the yarn sheet. The sensor and computer-controlled dye jets work together so that undyed areas and areas of unwanted overlap of dyes are virtually eliminated, reducing the amount of off-quality yarn produced versus conventional methods.
The invention is not limited as to the yarn that may be processed. Yarns of various sizes (deniers) and kinds, such as filament or spun, and of any fiber type, such as cotton, polyester or nylon, may be processed using the invention. The selection of jet size will vary according to the yarn size, yarn type, yarn composition, speed at which the yarn sheet is run, and pattern effects desired.
The present invention includes a dye overspray collection system that reduces the back-spatter of dye droplets or mist onto portions of the yarn sheet and reduces the quantity of dye that must be discarded due to the commingling of different color dyes. That portion of the dye sprayed in the direction of the yarn sheet that does not strike the sheet and that is not absorbed by the yarn (i.e., the overspray) is intercepted by a wire mesh screen, which reduces splatter onto the rearward-facing surface of the yarn sheet (opposite the dye jets) and allows the droplets to condense and flow down into a dye catch basin. The dye is then sent back to a dye tank, from which dye is drawn and pumped to the dye jet. A separate system is provided for each dye, thereby preventing commingling of different dyes and thereby reducing the amount of dye waste generated. This results in reduced dye costs and reduced costs in waste handling and disposal.
Yet another feature of the instant invention is a drip collection system. A drip collector is positioned under each dye jet to catch drips generated by the jets that might otherwise produce undesirable spotting on the yarn sheet. Dye caught by the drip collectors is directed into the dye catch basin and recirculated for use, as described above.
A further feature of the present invention is a vacuum exhaust system that collects dye mist (small airborne liquid particles of dye) that may be circulating near the yarn sheet, 111 thereby preventing spotting of the yarn sheet by the mist.
Still another feature is a drain which is part of the dye jet system. This drain clears air and foreign particles from the dye jet area, enabling the jet to function properly by reducing spatter and clogging.